# Forces in Truss Members (Statics)

cpmustang07

## Homework Statement

See attachment.
Edit: Point A is a pinned connection (has a reactionary force in X and Y direction). Point B is a roller connection (only has reactionary force in Y direction)

Sum Fx=0
Sum Fy=0
Sum of Moments=0

## The Attempt at a Solution

Find reaction forces at point A and D. Normally this wouldn't be an issue. I'd just find the reaction force of D by solving for the moment around point A. Then find A by knowing that the sum of forces in Y direction is 0. However, dimensions are not given in the problem. I have the answers, but I do not see how to get to them.

After finding reaction forces, isolate each joint and begin with joint with no more than two unknowns. Proceed until all forces are found.

#### Attachments

• 3-13.JPG
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## Answers and Replies

Homework Helper
Gold Member
These are all equilateral triangles...each horizontal member has the same length, L. What would be the perp. distance from the applied load to A?

cpmustang07
These are all equilateral triangles...each horizontal member has the same length, L. What would be the perp. distance from the applied load to A?

3*cos(60)*L, correct?

Staff Emeritus
Homework Helper
Gold Member
3*cos(60)*L, correct?
Interesting way to say 1.5L, which is correct.

Phrak
Interesting way to say 1.5L, which is correct.

No...

Homework Helper
Gold Member
No...
Why not?? If the length of each horizontal member is L, the perpendicular distance from the line of action of the applied load to A is 1.5 L.

Phrak
Why not?? If the length of each horizontal member is L, the perpendicular distance from the line of action of the applied load to A is 1.5 L.

right. 1.5L to A and 1.5KN on D.

cpmustang07
Thank you for your help guys. I'll work on it again today and see if this different train of thought will get me through it. :)

I got it guys. Thank you. Apparently I'm really slow. ;)

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